ES2791310T3 - Waste heat boiler system and method for cooling a process gas - Google Patents

Abstract

Waste heat boiler system (W) for cooling a process gas (220), comprising: a first shell and tube heat exchanger (2) for cooling the relatively hot gas (220) to the relatively hot gas (221) warm by allowing gas to flow through the tubes (13) of said first heat exchanger (2), the tubes (13) of which extend through a space (14) within a cover (25) of said first heat exchanger (2); an intermediate chamber (3) for receiving gas, cooled a relatively warm gas (221), exiting the tubes (13) of the first heat exchanger (2); and a second shell and tube heat exchanger (4) for cooling the relatively warm gas (221) further down to a relatively cold gas (222) by allowing gas to flow from the intermediate chamber (3) and through tubes ( 13 ') of the second heat exchanger (4), the tubes (13') of which extend through a space (14 ') within a cover (25') of said second heat exchanger (4), in which The intermediate chamber (3) is provided with an outlet (6) fluidly connected to a bypass channel (60) to allow a portion of the relatively warm gas (221) to enter said intermediate chamber (3) from the tubes ( 13) of the first heat exchanger (2) to divert the tubes (13 ') of the second deck and tube heat exchanger (4), in which both the bypass channel (60) and the tubes (13') of the Second shell and tube heat exchanger (4) are in fluid connection with a mixing chamber (10) to mix the relative gas (221) together. warmly flowing from the intermediate chamber (3) into the mixing chamber (10) through the bypass channel (60) and the relatively cold gas (222) coming out of the tubes (13 ') of the second exchanger (4 ) heat cover and tube.

Description

DESCRIPTION

Waste heat boiler system and method for cooling a process gas

The invention relates to a waste heat boiler system for cooling a process gas.

Waste heat boiler systems are known and are commonly used for cooling process gas, for example in plants producing hydrogen or synthesis gas, for example for industrial hydrogen production, methanol production, ammonia production, production of dimethyl ether, etc. Generally, the process gas to be cooled originates from, for example, a steam reformer, an autothermal reformer, a regenerative reformer or a partial oxidation unit. The process gas passing through the waste heat boiler system is generally charged to the waste heat boiler system at a relatively high temperature, for example, higher than 500 ° C, generally higher than 650 ° C, commonly even at 700 ° C or higher, for example, at a temperature between 700 ° C and 1000 ° C. The process gas that passes through the waste heat boiler system is generally charged to the waste heat boiler system at a relatively high pressure, for example, between 5 and 60 bar, such as 10 and 50 bar, such as between 20 and 35 bars.

The cooling medium used in waste heat boilers is usually water that evaporates on contact with a surface that acts as a physical boundary between said water and said process gas. For the applications described above, the water side pressure is generally pressurized to a pressure between 10 and 150 bars, more usually between 20 and 120 bars, such as between 35 and 70 bars.

The pressure difference between the process gas side and the water side is greater than 5 bar, generally greater than 10 bar and even greater than 25 bar in systems where the quality of the steam must be high (normally for ammonia and hydrogen).

Such process gas generally needs to be cooled to a relatively low temperature of 400 ° C or less, especially a temperature of less than 350 ° C, for example, for post-treatment of the gas, for example, catalytic treatment, especially displacement treatment gas from water, membrane separation, scrubbing or pressure change adsorption. For example, to facilitate the safe and proper operation of downstream units suitable for said after-treatment of the gas, known waste heat boiler systems are generally arranged to control the temperature of the relatively cold gas leaving said boiler system. known residual heat, such that said outlet gas can be of a predetermined temperature and / or be in a predetermined temperature range.

For example, a waste heat boiler system is known comprising a shell and tube heat exchanger for cooling relatively hot process gas having a temperature between 500 ° C and 1,000 ° C to a relatively cold gas having a temperature temperature less than 350 ° C by allowing process gas to flow through tubes of said shell and tube heat exchanger, which extend through a space within a shell of said shell and tube heat exchanger , through which space water is charged to cool said gas. Practical experience has shown that it can be nearly impossible to control the temperature of the relatively cold gas outlet through the shell and tube heat exchanger. In this regard, said known waste heat boiler system often comprises a bypass channel to allow a portion of the relatively hot gas to bypass the heat exchanger, see, for example, publications EP 1498678, EP 2312 252, US 4993367 and US 2007/0 125317, each of which discloses a central bypass channel extending through a center of the shell and tube heat exchanger. Said known waste heat boiler systems further comprise a mixing chamber for mixing said small amount of derived relatively hot process gas with the cooled process gas exiting the heat exchanger. To control the temperature of the relatively cold mixed gas which is fed from the waste heat boiler system to a downstream unit for gas treatment, said known waste heat boiler system further comprises a control system having a control valve to control the amount of by-pass relatively hot process gas.

However, a problem associated with such a prior art waste heat boiler system is that it suffers from corrosion problems due to mixing of relatively hot bypass gas with cooled process gas, which, as mentioned above, is performed for the sake of outlet temperature control. The temperature of the hot bypass gas is generally in the range of 500 ° C - 1000 ° C, at which temperatures metal dust or carburization corrosion occurs relatively easily. As a consequence, the prior art waste heat exchanger, especially its mixing chamber, its control valve, its control means for controlling its control valve, or other components of the waste heat boiler system, especially components located in or close to where mixing occurs, it can be relatively prone to corrosion. This can, for example, cause the control valve to jam. As a result of relatively severe corrosion, especially metal dust, prior art waste heat boiler systems are relatively portable and / or may or may even become unreliable.

From the patent of the United States 1,132,778, whose application was filed on July 11, 1910, a steam boiler and furnace is known that was destined, in those days, to the efficient production of steam or to the heating the water by utilizing the full length heating surfaces of the boiler shell and ducts and absorbing all available heat from the combustion products. In normal boiler and furnace operation, heated products of combustion pass from a hearth through upper ducts, which extend through the boiler shell, into a duct chamber. From said chamber, the combustion products pass through the lower ducts, which extend through a lower portion of said boiler cover, and then through a conduit under the lower part of said boiler cover into a chimney or so-called exhaust duct whose combustion products are discarded. To facilitate the starting of a furnace fire, a valve can be opened, thereby establishing a direct draft between the duct chamber and the chimney. Combustion products will pass from the upper ducts through the duct chamber and a pipe, which is provided with said valve and connects the duct chamber with the chimney, into said chimney without returning through the lower ducts. When the fire starts well, the valve closes and the products of combustion winding back and forth through and under the boiler cover, imparting their heat first to the hottest portions, then to the cooler, and finally to the the coldest portions of the water contained in the boiler.

It is an object of the invention to provide an alternative waste heat boiler system. In particular, it may be an object of the invention to provide a waste heat boiler system in which at least one of the disadvantages of the prior art waste heat boiler system is counteracted. More particularly, the invention may aim to provide a waste heat boiler system, especially a waste heat boiler system comprising a shell and tube heat exchanger, in which at least one of the aforementioned disadvantages is counteracted previously. In embodiments, the invention aims to provide a waste heat boiler system for cooling a relatively hot gas, for example, 500 ° C - 1,000 ° C or 700 ° C - 1,000 ° C to a relatively cold gas, in which on the one hand, the temperature of the relatively cold outlet gas, for example 400 ° C, preferably 350 ° C or less, can be controlled relatively well, and in which, on the other hand, the waste heat boiler system is relatively resistant to wear, for example relatively insensitive to metal dusting.

In addition, the present disclosure provides a waste heat boiler system for cooling a process gas, comprising a first shell and tube heat exchanger for cooling relatively hot gas to relatively warm gas by allowing gas to flow through tubes of said first heat exchanger, the tubes of which extend through a space within a shell of said first heat exchanger, said waste heat boiler system also comprises an intermediate chamber for receiving gas, cooled to relatively warm gas, exiting the tubes of the first heat exchanger, said waste heat boiler system further comprises a second shell and tube heat exchanger to cool the relatively warm gas to a relatively cold gas by allowing gas to flow from the intermediate chamber and through tubes of the second heat exchanger, the tubes of which extend through an es space within a shell of said second heat exchanger, wherein the intermediate chamber is provided with an outlet fluidly connected to a bypass channel to allow a portion of the relatively warm gas to enter said intermediate chamber from the tubes of the first heat exchanger for diverting the tubes of the second shell and tube heat exchanger, wherein the bypass channel and tubes of the second shell and tube heat exchanger are in fluid connection with a mixing chamber to mix together the Relatively warm gas flowing from the intermediate chamber into the mixing chamber through the bypass channel and relatively cool gas exiting the tubes of the second shell and tube heat exchanger.

By using at least two heat exchangers to cool relatively hot gas, for example 500 ° C -1,000 ° C, to a relatively cold gas, for example 350 ° C or less, gradually, and by extracting a portion of the semi-cooled gas to a relatively warm gas, for example 350 ° C - 500 ° C, and letting said portion bypass the second heat exchanger, the waste heat boiler system can mix relatively cold gas, for example , 350 ° C or less, with precooled gas, still relatively warm, for example 350 ° C to 500 ° C. Therefore, the waste heat boiler system can mix two relatively mild temperature gases, each having a relatively mild temperature, for example, each having a temperature below 500 ° C. Accordingly, a system can be provided that exclusively uses process gas streams at relatively mild temperatures, eg, 500 ° C or less, for outlet gas temperature control. Therefore, the mixing chamber of the waste heat boiler system can be facilitated not to receive any gas having a relatively high temperature, for example, above 500 ° C. As a result, the mixing chamber may be less prone to metal dusting and less prone to failure in the mixing chamber, as a result of which the waste heat boiler system may be relatively wear resistant and / or relatively trustworthy.

Advantageously, the bypass channel can be provided with a control valve to control the flow of relatively hot gas by diverting the tubes of the second heat exchanger. Therefore, the relatively warm gas flow, eg 350 ° C - 500 ° C, charged to the mixing chamber can be controlled in order to control the outlet temperature of the mixed gas leaving the mixing chamber. mixture. By providing the control valve in the bypass channel, one can counteract the control valve being subjected to relatively hot gas. As a result, failure of the control valve can be counteracted, for example due to metal dust on the valve and / or metal dust from the valve control means for controlling the valve.

The waste heat boiler system of the invention can therefore be relatively well protected, in a relatively elegant manner, from control valve failures and / or mixing chamber failures due to carburization or corrosion. Metal dust known to affect the relatively hot bypass channels and mixing chambers of conventional waste heat boiler systems.

Advantageously, the invention provides a heat exchanger system that can be optimized in terms of heat transfer area by performing the required cooling of the process gas in two stages, that is, in two or more shells in series. Both can be optimized for specific temperature levels. Thus, it allows the optimization of the total heat transfer surface by using different diameters and lengths of tube in each compartment, thereby reducing the total surface area required and therefore reducing the amount of steel.

In embodiments of the system of the present invention, at least a portion of the distal end of the pre-cooled warm gas bypass channel of the waste heat boiler system is formed by a sleeve extending into the mixing chamber, at wherein an inner wall surface of the mixing chamber is separated from an outer wall surface of said sleeve. As a result, the relatively warm gas flowing through said sleeve can, for example, disperse part of its heat, through the wall of said sleeve, to gas having a lower temperature, the gas of which is located between the surface from the outer wall of said sleeve and the inner wall surface of the mixing chamber, for example, the relatively cold gas entering the mixing chamber and / or the gas already mixed in the mixing chamber. Consequently, the relatively warm gas can be further precooled before it can come into contact with the inner wall of the mixing chamber. Additionally or alternatively, the sleeve can direct the relatively warm gas in a certain direction towards the mixing chamber, for example, in a direction substantially coaxial to a longitudinal direction of the mixing chamber, which can counteract the relatively hot gas from becoming it can mix with the relatively cold gas at least to some extent before it can come into contact with the inner wall of the mixing chamber. Therefore, metal dust in a gas mixing chamber can be counteracted even further.

For example, the mixing chamber may have a substantially elongated design, and the sleeve or the end portion thereof which extends into said mixing chamber may extend substantially coaxially with said mixing chamber.

Advantageously, the mixing chamber can be further provided with an inlet which is fluidly connected to the second heat exchanger, wherein said inlet is located substantially laterally to the side of the sleeve, so that during use of the boiler system of residual heat at least a portion, and preferably substantially all, of the relatively cold gas exiting the tubes of the second shell and tube heat exchanger enters the mixing chamber at a location substantially laterally to the side of said sleeve. As a result, a relatively large part of the gas that is present on the outside of the sleeve can be formed by a relatively cold gas charged from the second shell and tube heat exchanger to the mixing chamber, instead of being formed by mixed gas. whose temperature is lower than the temperature of the relatively warm gas. Furthermore, the introduction of at least a part of the relatively cold gas coming from the second heat exchanger into a space between the inner wall surface of the mixing chamber and the outer wall surface of the sleeve that extends into the mixing chamber. Mixing can facilitate that the gas in said space, which gas can be warmed by the gas flowing through the sleeve, will be renewed and / or can counteract the warm gas remaining in said space.

Advantageously, said sleeve extending into the mixing chamber, or at least a part thereof, especially a distal end portion which extends into the interior of the mixing chamber, can be replaceably mounted on the mixing chamber. Therefore, the replacement of such a sleeve, which can wear out faster than the inner wall of the mixing chamber, can be removed relatively easily, for example, without the need to remove all or a relatively large part of the mixing chamber. mixing, for example, to inspect, maintain, or replace said sleeve or part thereof.

In embodiments, the first shell and tube heat exchanger, the intermediate chamber, and the second shell and tube heat exchanger can be located in a main body of the waste heat boiler system, especially a container-shaped main body. , while the mixing chamber can then be located outside said main body. By locating the mixing chamber outside the main body of the waste heat boiler system, said mixing chamber, or one or more parts thereof or associated with it, such as a sleeve extending into the chamber mix, it can be inspected, replaced, maintained, cleaned or restored with relative ease.

It is noted that the location of the mixing chamber outside the main body of the waste heat boiler can also allow improved mixing of the process gas into a compact volume, while avoiding excessive mechanical stress by improved flow distribution. The location of the mixing chamber outside the main body can allow the prevention of metal dust in the waste heat boiler system.

Additionally or alternatively, the mixing chamber, or at least its outer wall, which may be formed at least in part of a container-like body, may be replaceably mounted in the waste heat boiler system, for example, to facilitate maintaining it.

By arranging that the bypass channel is an external channel, for example an external pipe, located outside the shell of the second shell and tube heat exchanger, and especially by locating said external channel substantially completely outside the main body of the boiler of waste heat, the bypass channel can be relatively well accessible, which can facilitate that, for example, it can be inspected, maintained, cleaned, replaced or restored relatively easily.

The external bypass channel located outside the main body of the waste heat boiler can facilitate the design to be simpler and / or the diameter of the cover to be smaller than in the case of a conventional bypass channel extending to through a heat exchanger and in parallel to the heat exchanger tubes. Additionally, providing the bypass channel outside the main body can reduce the differences between the expansion of the tubes and the expansion of the cover, which are proportional to the length of the tube and cover heat exchanger. Therefore, tube sheet failures due to mechanical stress caused by differential expansion can be counteracted.

However, in alternative embodiments, the bypass channel may be an internal channel that extends at least partially through the space within the shell of the second shell and tube heat exchanger, for example, to facilitate a relatively compact design of the tube. waste heat boiler system. In such a case, the internal bypass channel can be provided with an internal bypass valve.

Furthermore, the disclosure relates to a method for cooling a process gas. Said method comprises a step of providing a relatively hot process gas, and a step of cooling said relatively hot process gas to relatively warm gas by means of a first heat exchanger, preferably a shell and tube heat exchanger. The method further comprises a step of cooling a first portion of said relatively warm gas further down, that is, cooling it to relatively cold gas, by means of a second heat exchanger, preferably a second shell and tube heat exchanger. Additionally, the method comprises the steps of diverting a second portion of the relatively hot gas along said second heat exchanger; and mixing said relatively cold gas and said diverted portion of the relatively warm gas into a mixed gas. Advantageously, the method may also comprise a step of adjusting the flow of the second diverted portion of the relatively hot gas to control the temperature of the mixed gas, preferably to obtain a mixed gas of a substantially predetermined temperature, for example, a predetermined temperature corresponding to a desired inlet temperature of a downstream gas handling unit.

Advantageous embodiments according to the invention are described in the appended claims.

By way of non-limiting example only, embodiments of the present invention will now be described with reference to the accompanying figures in which:

Figure 1 shows a schematic cross-sectional view of an embodiment of a waste heat boiler system in accordance with one aspect of the invention; Y

Figure 2 shows a schematic cross-sectional view of an example of an advantageous mixing chamber not in accordance with one aspect of the invention.

It is noted that the figures show merely preferred embodiments in accordance with the invention, and that the figures are provided by way of examples only and are to be understood as such. In the figures, the same or similar reference signs or numerals refer to the same or corresponding parts.

Figure 1 shows a schematic cross-sectional view of an embodiment of a waste heat boiler system W according to one aspect of the invention.

The waste heat boiler system W according to the invention can be arranged to be used to cool the process gas 220, for example in a plant producing hydrogen or synthesis gas, for example for the industrial production of hydrogen, methanol production, ammonia production, dimethyl ether production, etc. It is noted that the relatively hot process gas 220 to be cooled by the waste heat boiler system W, which gas during use passing through the waste heat boiler system W, can originate, for example, from a steam reformer, an autothermal reformer, a regenerative reformer, or a partial oxidation unit.

For example, the relatively hot gas 220 to be cooled by the waste heat boiler system W may initially be at a temperature of at least 500 ° C, preferably at least 650 ° C, especially at least 700 ° C. Additionally or alternatively, the temperature of said relatively hot gas may be at most 1,200 ° C, preferably at most 1,100 ° C, such as at most 1,000 ° C.

During use, the waste heat boiler system W can cool the gas to be cooled to a temperature lower than 350 ° C, for example, for gas treatment in a location downstream of the waste heat boiler system W. Said gas treatment can, for example, be or comprise a catalytic treatment such as water gas displacement treatment or membrane separation, by scrubbing or by pressure change adsorption. It is noted that the temperature of the gas 223 from the waste heat boiler W can be, for example, critical for the safe and proper operation of a respective downstream unit and / or for the controlled generation of steam. For example, therefore, it may be desired to control the outlet gas temperature relatively well.

As can be seen in Figure 1, the present waste heat boiler system W for cooling a process gas comprises a first shell and tube type heat exchanger 2. Said first shell and tube heat exchanger 2 is for cooling relatively hot gas 220 to relatively warm gas 221 by allowing gas to flow through tubes 13 of said first heat exchanger 2, wherein said tubes 13 extend to through a space 14 within a cover 25 of said first heat exchanger 2.

Advantageously, the waste heat boiler system W can also comprise an inlet chamber 1 in fluid connection with the upwardly directed ends of the tubes 13 of the first heat exchanger 2, the chamber 1 of which may further comprise an inlet 11 to allow relatively hot gas enters the inlet chamber 1, and into the waste heat boiler system W in case the inlet chamber 1 is the most upward part of the waste heat boiler system W. A wall or Cover 12 defining the inlet chamber 1, which can, for example, be made of steel or other metal or alloy, can preferably be lined with refractory material to prevent the material of said wall or cover 12 from being exposed to some extent to excessive temperature and stress due to high inlet gas temperature. The inlet chamber 1 may be provided with multiple outlets to allow the relatively hot gas 220 to flow from said chamber 1 to the respective tubes 13 of the first heat exchanger 2.

During use of the waste heat boiler system W, the relatively hot process gas flows through the tubes 13 of the first heat exchanger 2 in which the heat can be transferred to a cooling fluid, such as water, which flows through the space 14 defined by the cover 25 and whose cooling fluid contacts the outer surface of said tubes 13.

The waste heat boiler system W also comprises an intermediate chamber 3 for receiving gas, cooled to relatively warm gas 221, exiting the tubes 13 of the first heat exchanger 2.

Additionally, the waste heat boiler system W comprises a second shell and tube heat exchanger 4, which is to cool the relatively warm gas 221 further down to the relatively cold gas 222 allowing gas to flow from the intermediate chamber 3 and through tubes 13 'of the second heat exchanger 4, the tubes 13' of which extend through a space 14 'within a cover 25' of said second heat exchanger 4.

In the respective exchanger 2; 4 cover and tube heat, the cooling fluid, for example, water, can enter the cover 25; 25 'respective through one or more inputs 15; 15 ', which can be connected to so-called downspouts, and can come out of said cover 25; 25 'through one or more outlets 16; 16 ', which can be connected to so-called risers. For example, because the cooling liquid that absorbs heat from the gas to be cooled can at least partially, and preferably substantially completely, be converted to gas, for example steam, at the one or more outlets 16; 16 'may be located on an upper side of cover 25; 25 'respective. Additionally, the one or more entries 15; 15 'may be located on a substantially opposite side, eg, on or near a lower side, of said cover 25; 25 '.

Advantageously, the cover 25 can be equipped with one or multiple vents 17; 17 ', for example, to avoid the formation of steam, for example, the uppermost of the tubes 13; 13 'of the respective exchanger 2; 4 heat cover and tube)

Advantageously, one or more outlets 18 may be provided; Boiler system purge 18 ', for example, on a lower side of cover 25; 25 'of exchanger 2; 4 of respective heat, to allow intentionally wasting some cooling liquid, eg water, from space 14; 14 'on said deck 25; 25 'to counteract a relatively high concentration or build-up of impurities such as solids, for example, during continuous vapor evaporation. Said boiler system purge outlets 18: 18 'may for example be formed by flange connections and may facilitate an intermittent purge system to remove accumulated solids from inside the respective cover.

The intermediate chamber 3 is provided with an outlet 6 which is fluidly connected to a bypass channel 60 to allow a part of the relatively warm gas 221 to enter said intermediate chamber 3 from the tubes 13 of the first heat exchanger 2 to avoid the tube 13 'of the second shell and tube heat exchanger 4. Both the bypass channel 60 and the tubes 13 'of the second shell and tube heat exchanger 4 are in fluid connection with a mixing chamber 10 for mixing together the relatively warm gas 221 flowing from the chamber 3 intermediate the mixing chamber 10 through the bypass channel 60 and the relatively cold gas 222 exits the tubes 13 'of the second shell-and-tube heat exchanger 4.

Therefore, the temperature of the relatively cold gas 222 coming from the second heat exchanger 4 can be raised to some extent by mixing it with the relatively warm gas 221, rather than mixing it with the relatively hot gas 220 as is done in boiler systems. prior art waste heat. As a result, it will be counteracted that the mixing chamber 10 will be exposed to gases of relatively high temperatures, eg, temperatures above 500 ° C, eg, temperatures between 700 ° C and 1,000 ° C.

It is noted that the tubes 13 'of the second shell-and-tube heat exchanger 4 can supply the relatively cold gas 222, for example, to an outlet chamber 5, and that said outlet chamber 5 may be connected, for example, in fluidly with the mixing chamber 10 through a connecting channel 8 connecting an outlet 7 of the outlet chamber 5 with an inlet 101 of the mixing chamber 10.

Furthermore, it is noted that the first shell and tube heat exchanger 4, the intermediate chamber 3 and the second shell and tube heat exchanger 4 can be provided in a waste heat boiler main body, especially a main body in container shape. Advantageously, as can be seen in the exemplary embodiment of Figure 1, the waste heat boiler main body in the embodiments may also comprise the inlet chamber 1 and / or the outlet chamber 5. The outer wall or cover of the main body 12, 25, 32, 25 ', 52 of the waste heat boiler, can advantageously be formed at least partially by the cover 25 of the first heat exchanger 2, an outer wall 32 of the chamber 3 intermediate, and the cover 25 'of the second heat exchanger 4. Additionally, the outer walls 12, 52 of the inlet chamber 1 and / or the outlet chamber 5 may define, for example, parts of the main body 12, 25, 32, 25 ', 52 of the waste heat boiler.

Advantageously, the bypass channel 60 may be provided with a control valve 9 or a so-called bypass valve 9 to control the flow of relatively warm gas 221 bypassing the tubes 13 'of the second heat exchanger 4. Therefore, said valve 9 can be used to adjust the flow rate of said portion of relatively hot process gas exiting the intermediate chamber 3 through the bypass channel 60, allowing temperature control of the outlet gas 223 of the residual boiler system W.

By placing said bypass valve 9 outside the intermediate chamber 3 and / or outside the main body of the system, the bypass valve 9 can be relatively easy to access for maintenance purposes.

Although the bypass channel 60 may preferably be formed as an external channel, for example an external tube, provided outside the shell 25 'of the second shell and tube heat exchanger 4, and preferably outside the body 12, 25, 32 , 25 ', 52 of the waste heat boiler, the bypass channel may be formed in alternative embodiments as an internal channel extending at least partially through the space 14' within the cover 25 'of the second heat exchanger 4 cover and tube heat, for example, to facilitate a relatively compact design of the residual heat boiler system W. In the latter case, said internal channel can be relatively wide with respect to a single tube 13 'of the second heat exchanger 4 shell and tube, and / or said internal channel can be relatively well thermally insulated with respect to tubes 13 'of the second shell and tube heat exchanger 4, that is, said tube 13' is t Thermally conductive relatively well with respect to said internal channel.

In preferred embodiments, the mixing chamber 10 can be located outside of the main body 12, 25, 32, 25 ', 52 of the waste heat boiler. However, in alternative embodiments, the mixing chamber 10 may be located within the waste heat body 12, 25, 32, 25 ', 52 main boiler. For example, the mixing chamber 10 can be located inside and / or can be formed by the outlet chamber 5, for example, when the bypass channel is formed as an internal bypass channel extending through the second exchanger. 4 cover and tube heat.

With respect to exchangers 2; 4 of cover and tube heat, it is observed that, in the embodiments, the exchangers 2; 4 can be provided with tube plates 20 that can form an edge between the respective exchangers 2; 4 heat and a respective chamber 1; 3 in a downward direction or a respective chamber 3; 5 in the upward direction. The tube plates 20 may be provided with holes connected to the chamber 1; 3; 5 respective with the respective tubes 13; 13 'to allow gas to flow from the respective chamber into said tubes or from said tubes into the respective chamber, respectively.

The tubes can be hermetically connected to the respective chamber by means of the respective tube plate 20. Additionally, the tubes may be supported by support plates 21 or so-called baffles 21 provided within exchanger 2; 4 respective heat. Advantageously, the flowing coolant can be distributed substantially equally in the axial direction of the shell and tube heat exchanger by means of said baffles or support plates 21 and / or by means of flow distribution plates 19 or other of devices 19 arranged for an optimal distribution of the flow through the cover 25; 25 'of the respective heat exchanger.

Although the second shell and tube heat exchanger 4 may have substantially the same design as the first shell and tube heat exchanger 2, and although both heat exchangers 2; 4 heat can be substantially equipped with the same characteristics 25; 25 ', 13; 13 ', 15; 15 ', 16; 16 ', 17; 17 ', 18; 18 ', 19; 19 ', 20, the dimensions of both exchangers 2; 4 heat may differ from each other. For example, the length and / or the diameter of the cover and / or the length, the diameter and / or the number of the tubes may be different. Since the gas flowing through the second shell and tube heat exchanger is of a lower temperature, the cross-sectional surface area of the tubes 13 'of the second heat exchanger, and hence the diameter of the second heat exchanger can be relatively small with respect to the first heat exchanger. Additional or alternatively, the design of the baffle can be different.

Furthermore, it is noted that, although the tubes have a substantially straight design in the exemplary embodiment shown in Figure 1, the tubes may have another design, for example, a U-shaped design. Alternatively or additionally, the baffles 21, which are in the exemplary embodiment designed to allow water to flow substantially transverse to the tubes, eg substantially upward, they may have a different design in alternative embodiments. For example, the baffles can be positioned to define a serpentine path, for example, of a one-pass straight tube heat exchanger, for example, allowing the coolant, preferably water, to flow substantially in the opposite direction of the gas flowing through the tubes

The system comprises a first and a second shell and tube heat exchanger. Each shell and tube heat exchanger typically comprises at least one shell and multiple tubes. Commonly, the cover and tubes of the first heat exchanger are separated from the cover and tubes of the second heat exchanger by the intermediate chamber. The first heat exchanger is generally located substantially longitudinally next to the second heat exchanger, in particular in a longitudinal direction of the tubes. Therefore, the second heat exchanger is adjacent to the first heat exchanger in a longitudinal direction of the tubes of the first heat exchanger, separated from each other by the intermediate chamber (and optionally the tube plates if present).

As best seen in Figure 2, which shows a mixing chamber 10 corresponding to the mixing chamber 10 of the waste heat boiler system W of Figure 1, in embodiments of a waste heat boiler system W according to With the invention, the mixing chamber 10 can be formed as a mixing tee 10.

Preferably, the mixing chamber 10 is designed such that relatively warm gas 221 enters the mixing chamber 10 through a reducing piece 109 having a reduced diameter relative to the bypass channel 60 and / or relative to to mixing chamber 10. Therefore, the relatively warm gas 221 flowing from said bypass channel 60 into the mixing chamber 10 can blow into the mixing chamber 10 relatively centrally, thus counteracting direct contact with the wall of the chamber. 10 mixing, and thus counteracting the stresses of the material mechanically imposed in the mixing chamber 10, for example, due to differences in temperature.

Additionally or alternatively, at least a portion of the distal end of the bypass channel 60 may be formed by a sleeve 105 that extends into the interior 110 of the mixing chamber 10. An inner wall surface 106 of the mixing chamber 10 can then be separated from an outer wall surface 105 'of said sleeve 105. As a result, the relatively warm gas 221, which comes from the intermediate chamber 3, and flows through of said sleeve 105, it can disperse part of its heat through the wall of said sleeve 105, to gas having a lower temperature, gas that is between the surface of the outer wall 105 'of said sleeve 105 and the surface 106 inside wall of mixing chamber 10. As a consequence, the relatively warm gas 221 coming from the intermediate chamber 3 can be further precooled before it can come into contact with the inner wall 106 of the mixing chamber 10. Therefore, the metal dust in the mixing chamber 10 can be largely countered.

The diameter of the sleeve 105 and / or the distance between said sleeve 105 and the inner wall 106 of the mixing chamber 10 can be chosen so that the relatively warm gas 221 flowing out of said sleeve 105 can be counteracted from contacting the mixing chamber wall material prior to being mixed with the relatively cool gas 222, thereby counteracting the stress of the mixing chamber wall material. In this way, the relatively hot gas 221 can concentrate in the center of the mixing chamber 10 and can undergo mixing and heat exchange with the relatively cold process gas 222, which preferably flows substantially coaxially. Fine-tuning the diameter of the mixing chamber and the velocity of both the relatively hot process gas and the relatively cold process gas can allow mixing of the gas in a relatively small-sized mixing chamber, while avoiding excessive stresses in the mixing chamber material.

Preferably, the diameter of the sleeve 105 and the diameter of the wall of the mixing chamber 10 are selected such that the relatively hot process gas flow can be mixed relatively homogeneously with the relatively cold process gas before it exits. from the mixing chamber 10, for example, through a reducing piece 103 near the end of the mixing chamber.

Advantageously, the mixing chamber 10 may be provided with an inlet 102 fluidly connected to the second shell and tube heat exchanger 4, said inlet 102 being located substantially laterally to the side of the sleeve 105, so that during use of the system residual heat boiler W al Less a part, and preferably all, of the relatively cold gas 222 exiting the tubes 13 'of the second shell and tube heat exchanger 4 enters the mixing chamber 10 at a location substantially laterally adjacent to said sleeve 105 As a result , the temperature of a portion of gas present in mixing chamber 10 and outside of sleeve 105 may be relatively cold and / or said portion of gas may be relatively easily cooled.

The mixing chamber 10 comprises an inlet sleeve 105 for relatively hot or relatively hot gas, said sleeve 105 extending into the interior 110 of the mixing chamber 10, wherein a surface of the interior wall 106 of the mixing chamber 10 is separated from a surface of the outer wall 105 'of said sleeve 105, in which the mixing chamber 10 is provided with an inlet 101 to allow relatively cold gas to enter the mixing chamber 10, in which said inlet 101 is located substantially laterally to the side of said sleeve.

As can be seen from the figures, the mixing chamber 10 may have a substantially elongated design. Advantageously, the sleeve 105 or at least an end portion thereof that extends within said mixing chamber 10 may extend substantially coaxially with said mixing chamber 10, for example, with a wall circumscribing the interior 110 of the mixing chamber 10. mixture.

Additionally or alternatively, an end portion 103 of mixing chamber 10, preferably of a substantially elongated mixing chamber, may be provided with an outlet 107 to allow gas 223 mixed in said mixing chamber 10 to flow out of said chamber. 10 mixing chamber, wherein the surface area covered by a cross section of said end portion 103 of mixing chamber 10 is reduced towards said outlet 107, preferably in a substantially gradual manner. It is noted that the end portion 103 can be formed, as well as a reducing piece 103.

In embodiments, the mixing chamber 10 may comprise an outer wall having an internal diameter that is set as a function of both the mass flow of the relatively warm gas and the mass flow of the relatively cool process gas and as a function of the velocities of entry of both said gases and the exit velocity of the final mixed gas. The diameter of the mixing chamber 10 can be selected so that the flow distribution in said mixing chamber 10 is relatively homogenized, for example, to avoid excessive stress on the material.

The mixing chamber 10 is used in an embodiment of the waste heat boiler system W having a bypass channel 60 which bypasses the second shell and tube heat exchanger 4 as described above, the mixing chamber 10, as described mentioned above, it can also be used in other waste heat boiler system. For example, the inlet 101 for relatively cold gas may be in fluid connection with gas outlets formed by the ends of the tubes of a shell and tube heat exchanger of said alternative waste heat boiler system, and the sleeve 105 of inlet for relatively hot gas or for relatively hot gas, for example, may be in fluid connection with an inlet chamber provided upstream of said shell and tube heat exchanger of said alternative waste heat boiler system by means of a bypass channel. Preferably, said bypass channel can be provided with a control valve, more preferably a control valve resistant to high temperatures, as said bypass channel can in said embodiments of the mixing chamber 10 receive relatively hot gas, for example, at a temperature above 500 ° C, above 650 ° C, or even above 700 ° C, which is not precooled.

A waste heat boiler system is designed to withstand high temperatures and high pressures, typically found in process gas cooling. According to the above, the inlet for supplying the system with process gas (for example, inlet 11) is commonly lined with refractory, since the process gas entering the system is normally between 700 and 950 ° C.

The tubes and / or tube sheets are designed to allow them to accommodate large temperature differences. Preferably, the tubes and / or the tube sheets are thin and to some extent flexible. The thin sheet tube design is based on the theory of the flexible membrane held in place by the tubes, so the tubes must be in tension. From a mechanical point of view, the pressure in the tubes (that is, the process gas side) is preferably less than the pressure in the cover (that is, the water side) of the heat exchanger. The high pressure on the inner surface of the tubes would cause the tubes to compress (eventually eccentric compression), which would lead to an undesirable amount of tension in the tubes. The pressure on the process gas side, the pressure on the water side, and the pressure difference between the two can be as described above for general waste heat boiler applications.

The first shell and tube heat exchanger, the intermediate chamber, and the second shell and tube heat exchanger may be located in a main body of the waste heat boiler system, especially a container-shaped main body. The container-shaped main body preferably has a substantially elongated design. Such a design is suitable to withstand high pressures and high temperatures normally found in process gas cooling. In addition, it will provide an acceptable and gradual heat distribution throughout the system.

In the case of an elongated design, the first heat exchanger is generally located substantially longitudinally to one side of the second heat exchanger. Accordingly, the second heat exchanger is generally adjacent to the first heat exchanger in a longitudinal direction of the elongated main body, with the exchangers separated from each other by the intermediate chamber (and optionally the tube plates if present) . Therefore, the intermediate chamber is normally placed in the middle portion of the elongated main body, with the first heat exchanger located on one side of the intermediate chamber towards one end of the elongated main body and the second heat exchanger located on the other. side of the intermediate chamber towards the other end of the elongated main body. Such a design also provides easy maintenance as the coldest parts of the waste heat boiler, in particular the outlet chamber and / or the mixing chamber, are well accessible. It is generally recognized in the art that potassium leached from the reforming catalyst contributes to tube corrosion in the cooler part of a conventional waste heat boiler.

Preferably, each of the first and second shell and tube heat exchanger is provided with at least two tube sheets. Typically a tube sheet is provided at both ends of the heat exchanger. Therefore, the first and second heat exchanger essentially constitute two separate compartments. This design has the advantage of reducing stresses induced by expansion of the differential tube, especially compared to a single shell or single heat exchanger design. The flexibility of having two separate shell and tube heat exchangers allows for high cooling capacity.

In one aspect, the invention also relates to a method for cooling a process gas, which method can preferably be carried out by means of a waste heat boiler system W according to another aspect of the invention.

In this method, a relatively hot process gas 220 can be provided, for example at a temperature higher than 500 ° C, preferably higher than 650 ° C, especially 700 ° C or higher. Such relatively hot process gas 220 may originate, for example, from a steam reformer, an autothermal reformer, a regenerative reformer, or a partial oxidation unit. In a second stage, said relatively hot process gas 220 is cooled to relatively warm gas 221, for example, relatively warm gas 221 of 550 ° C or less, especially 500 ° C or less, for example, by means of a first exchanger. 2 heat exchanger, preferably a shell and tube heat exchanger 2, such as, for example, a heat exchanger 2 which is part of a waste heat boiler system W as described above.

The process gas that passes through the waste heat boiler system is generally charged to the waste heat boiler system at a relatively high pressure, for example between 5 and 60 bar, commonly between 10 and 50 bar, such as 20 and 35 bar.

In a third stage, a first portion or first fraction of said relatively warm gas 221 is further cooled by means of a second heat exchanger, preferably a second shell and tube heat exchanger 4, such as for example a heat exchanger 4 it is part of a waste heat boiler system W as described above. For example, it is cooled down to a relatively cold gas 222, for example, a gas 222 having a temperature of 400 ° C or less, especially 350 ° C or less.

A second portion or second fraction of the relatively warm gas 221 is bypassed along said second heat exchanger 4.

Additionally, the method comprises a step of mixing said relatively cold gas 222 and said diverted portion of the relatively warm gas 221 together into a mixed gas 223, preferably at a location outside the main body of the waste heat boiler.

Advantageously, the method may comprise a further step of adjusting the flow of the second diverted portion of the relatively hot gas, for example, by means of a control valve 9, to control the temperature of the mixed gas 223, preferably in order to obtain a mixed gas of substantially a predetermined temperature.

It is noted that the method may further comprise steps of detecting the temperature of the outlet gas 223, detecting the temperature of the relatively hot gas 220, detecting the temperature of the relatively cold gas 222, and / or detecting the temperature of the gas 221. relatively hot, and / or the steps of sensing the flow rate (s) of one or more of the respective gas flows, for example, a mass flow of the respective gas, to control the temperature of the outlet gas 223, for example by controlling or adjusting the control valve 9 at least in part based on one or more of said sensed parameters and / or a desired outlet gas temperature. For example, the waste heat boiler system W may be provided with one or more controllers and / or sensors. Furthermore, the bypass valve 9 may be equipped with an actuator, and preferably also a positioner and / or a position sensor, to control the position of the bypass valve in order to allow a controlled amount of the relatively warm gas 221 exiting the intermediate chamber 3 flow into the mixing chamber 10.

In a preferred embodiment, the regulated flow rate of the bypass relatively hot gas may depend on the temperature measured from the relatively cold gas 222 fed to the mixing chamber 10, for example, through the connecting channel 8.

It is noted that, for purposes of clarity and concise description, the features are described herein as part of the same or different embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

In the present disclosure, any combination of parts of the disclosed embodiments is also considered to have been disclosed. For example, parts that are only explicitly described as part of a waste heat boiler system having a bypass channel extending from an intermediate chamber between two shell and tube heat exchangers into said mixing chamber are also disclosed in the present disclosure as part of a mixing chamber as such, the mixing chamber of which is not necessarily used and / or will be used in said waste heat boiler system.

Additionally, it is noted that the invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

For example, the system may comprise multiple first shell and tube heat exchangers, in which additional intermediate chambers may be provided between adjacent ones of said multiple first shell and tube heat exchangers. Additionally or alternatively, the system may comprise multiple second shell and tube heat exchangers, in which additional intermediate chambers may be provided between adjacent said multiple second shell and tube heat exchangers. Then, one or more bypass channels may be arranged to divert relatively warm gas from one or more of said intermediate chambers, for example, from at least one intermediate chamber provided between the or the last first heat exchanger and the first or second heat exchanger, towards the mixing chamber. Providing multiple first and / or multiple second heat exchangers can, for example, overcome tube and / or cover length limitations. The differential growth between the cover and the tubes can be considerably reduced and relatively large boiler systems can be built without excessive mechanical stress on the respective heat exchanger.

As another example, the heat exchangers in the system may have a tube sheet peripheral configuration, for example, comprising knuckles, but alternatively they may have a rigid peripheral configuration, for example, lacking such knuckles.

Claims (13)

1. Residual heat (W) boiler system to cool a process gas (220), comprising: a first shell and tube heat exchanger (2) for cooling relatively hot gas (220) to relatively warm gas (221) by allowing gas to flow through tubes (13) of said first exchanger (2) heat, the tubes (13) of which extend through a space (14) inside a cover (25) of said first heat exchanger (2); an intermediate chamber (3) to receive gas, cooled a relatively warm gas (221), exiting the tubes (13) of the first heat exchanger (2); Y a second shell and tube heat exchanger (4) for cooling the relatively warm gas (221) further down to a relatively cool gas (222) by allowing gas to flow from the intermediate chamber (3) and through tubes (13 ') of the second heat exchanger (4), the tubes (13') of which extend through a space (14 ') within a cover (25') of said second heat exchanger (4), wherein the intermediate chamber (3) is provided with an outlet (6) fluidly connected to a bypass channel (60) to allow a portion of the relatively warm gas (221) to enter said intermediate chamber (3) from the tubes (13) of the first heat exchanger (2) to divert the tubes (13 ') of the second shell and tube heat exchanger (4), in which both the bypass channel (60) and the tubes (13 ') of the second shell and tube heat exchanger (4) are in fluid connection with a mixing chamber (10) to mix together the relatively warm gas (221) that flows from the intermediate chamber (3) into the chamber (10 ) of mixing through the bypass channel (60) and the relatively cold gas (222) coming out of the tubes (13 ') of the second shell and tube heat exchanger (4). 2. Waste heat boiler system (W) according to claim 1, wherein the first shell and tube heat exchanger (2), the intermediate chamber (3) and the second heat exchanger (4) of tube and cover are located in a main body of elongated design and the first heat exchanger (2) is located substantially longitudinally to one side of the second heat exchanger (4); I wherein the bypass channel (60) is provided with a control valve (9) for controlling the flow of relatively warm gas (221) diverting the tubes (13 ') of the second heat exchanger (4). Residual heat boiler system (W) according to any one of the preceding claims, wherein at least a portion of the distal end of the bypass channel (60) forms a sleeve (105) extending into the interior (110) of the mixing chamber (10), and wherein a surface (106 ) of the internal wall of the mixing chamber (10) is separated from an external wall surface (105 ') of said sleeve (105), preferably wherein the mixing chamber (10) is provided with an inlet (102) fluidly connected to the second shell and tube heat exchanger (4) and said inlet (102) is located substantially laterally to one side of the sleeve (105) in such a way that during use of the waste heat boiler system (W) at least a portion of the relatively cold gas (222) exits the tubes (113 ') of the second deck heat exchanger (4) and tube enters mixing chamber (10) at a location substantially laterally to one side of said sleeve (105). 4. Waste heat boiler system (W) according to claim 3, wherein the mixing chamber (10) is of substantially elongated design, and wherein the sleeve (105) or the end portion thereof extending into said mixing chamber (10) extends substantially coaxially with said mixing chamber (10). Waste heat boiler system (W) according to any one of the preceding claims, wherein an end portion (103) of the mixing chamber (10), preferably of a mixing chamber (10), is provided substantially elongated mixing, with an outlet (107) to allow gas (223) mixed together in the mixing chamber (10) to flow out of said mixing chamber (10), and wherein the surface area covered by a cross section of said end portion (103) of mixing chamber (10) tapers towards said outlet (107), preferably in a substantially gradual manner. Waste heat boiler system (W) according to any one of the preceding claims, in which the first shell and tube heat exchanger (2), the intermediate chamber (3) and the second exchanger (4) shell and tube heat pipes are located in a main body, especially a main body (12, 25, 32, 25 ', 52) in the shape of a glass, in which the mixing chamber (10) is located outside said body (12, 25, 32, 25 ', 52) main. Waste heat boiler system (W) according to any one of the preceding claims, in which the bypass channel (60) is an external channel provided outside the cover (25 ') of the second exchanger (4) of cover and tube heat, and preferably outside the main body (12, 25, 32, 25 ', 52). Waste heat boiler system (W) according to any one of claims 1-6, wherein the bypass channel (60) is an internal channel extending through the space (14 ') within the cover (25 ') of the second cover and tube heat exchanger (4). Waste heat boiler system (W) according to claim 8, wherein said internal channel is relatively wide with respect to a tube (13 ') of the second shell and tube heat exchanger (4), and /or wherein said internal channel is thermally insulated relatively well with respect to a tube (13 ') of the second shell and tube heat exchanger (4), that is to say said tube (13') is thermally conductive relatively well with respect to said internal channel. 10. Waste heat boiler system (W) according to any one of the preceding claims, the mixing chamber (10) comprises an inlet sleeve (105) for relatively warm or relatively hot gas (221), said sleeve ( 105) extends into the interior (110) of the mixing chamber (10), wherein an inner wall surface (106) of the mixing chamber (10) is separated from an outer wall surface (105 ') of said sleeve (105), wherein the mixing chamber (10) is provided with an inlet (101) to allow relatively cold gas (222) to enter the mixing chamber (10), wherein said inlet (101) is located substantially laterally to one side of said sleeve (105). A waste heat boiler system (W) according to claim 10, wherein the mixing chamber (10) is of substantially elongated design and the sleeve (105) or an end portion thereof extends substantially coaxially. with said substantially elongated mixing chamber (10); I wherein the inlet (101) for relatively cold gas (222) is in fluid connection with gas outlets formed by the ends of the tubes (13 ') of a shell and tube heat exchanger (4) of a heating system. waste heat boiler (W) and the inlet sleeve (105) for relatively warm gas or relatively hot gas (221) is in fluid connection with an inlet chamber (3) provided upstream of said heat exchanger (4) cover and tube of said waste heat boiler system (W) by means of a bypass channel (60), preferably said bypass channel (60) is provided with a control valve (9), more preferably a valve ( 9) High temperature resistant control. 12. Method for cooling a process gas (220), comprising the steps of: providing a relatively hot process gas (220) at a temperature above 500 ° C, preferably above 650 ° C, especially at or above 700 ° C; cooling said relatively hot process gas (220) to relatively warm gas (221), for example relatively warm gas (221) of 550 ° C or less, especially 500 ° C or less, by means of a first exchanger (2 ) heat, preferably a shell and tube heat exchanger (2); cooling a first portion of said relatively warm gas (221) further down, i.e. cooling to relatively cold gas (222), for example gas (222) having a temperature of 400 ° C or less, especially 350 ° C or less , by means of a second heat exchanger (4), preferably a second shell and tube heat exchanger (4); diverting a second portion of the relatively warm gas (221) along said second heat exchanger (4); Y mixing said relatively cold gas (222) and said diverted portion of the relatively warm gas (221) together into a mixed gas (223). 13. Method according to claim 12, wherein the method further comprises the step of adjusting the flow of the second diverted portion of the relatively warm gas (221) to control the temperature of the mixed gas (223), preferably in order to obtain a mixed gas (223) of substantially a predetermined temperature; I wherein the method is conducted in a waste heat boiler system (W) according to any one of claims 1-11.